1. Field of the Invention
This invention relates to a tool carousel for use in a tool changer on a machining centre.
2. Background Art
A tool carousel comprises a wheel-like structure which, in use, carries a series of individually removable tools. In most cases, the carousel comprises a rotational index means, so as to enable any selected one of the tools carried by the carousel wheel to be located at a predetermined rotational position, whereat a transfer mechanism can present the selected tool to a machine tool for use in a machining operation.
FIG. 1 shows a typical example of a machining centre which includes a tool carousel. As can be seen, the tool carousel wheel 1 is mounted upon a horizontal rotational axis adjacent a transfer mechanism 2. Referring to FIG. 2, it will be seen that the transfer mechanism 2 comprises a transfer arm 4 for transferring tools between the carousel wheel 1 and a machine tool spindle 3. The transfer arm rotates about a central rotation axis 8 and has a tool grip at each end.
As can be best seen in FIG. 3, the carousel wheel 1 comprises a plurality of circumferentially consecutive pots 6, each of which is used for storing a respective tool. In the storage position, each of the pots orientates its respective tool with its axis generally horizontal. However, when a tool is specified by the machine control, the carousel wheel 1 is rotated until the correct tool is located in the transfer position 5, and the pot containing this tool is then rotated through 90.degree. about a horizontal axis which is perpendicular to the rotational axis of the carousel wheel. As a consequence, the pot hangs vertically down and in the manner of the pot designated 7. In this position, the tool has its axis parallel to the centre line of the machine tool spindle 3. Once the pot is in this position, the transfer arm 4 is able to rotate about its vertical rotation axis 8 and remove the selected tool from its pot 7 whilst simultaneously removing any existing tool from the spindle nose 3. As it continues to rotate, the position of the two tools is reversed, the selected tool is presented to the spindle nose, and the deselected tool is presented to the appropriate pot on the carousel 1. That pot is then rotated back up through 90.degree., so that the deselected tool is stored with its axis inclined horizontally, in common with the other tools stored in the carousel.
Tools for use in a machine tool are invariably heavy, metal items and the carousel wheel of a tool carousel therefore has to be strong and sturdy enough to carry all of the tools without buckling or breaking over a long period of time during which the tool carousel is required to operate reliably, without breakdown. It has therefore been the practice to form carousel wheels of known tool carousels from metal.
FIG. 4 shows a vertical section through a known tool changer incorporating such a carousel. From the figure, it can be seen that a pot 105 has a generally cylindrical form and is attached to the hub 124 of a carousel wheel via a rotation axis 117. The pot 105 is fitted with a collar 119 at an end thereof which is situated at the top of the pot when it is rotated through 90.degree. about the axis 117 at the tool access position, as shown in dotted lines in FIG. 4. Axially inwardly of the collar 119, there is located a retention collar 104 that comprises a central axial bore into which a number of balls 100 are resiliently urged to project. In use, a pull-stud of a tool holder is located within the bore and gripped by the balls 100. When the tool is to be extracted, this is achieved by axial displacement of an extractor 118 which can be axially pushed into the bore, to force the pull-stud out.
A dog 102 is provided in the mouth of the pot 105 for retaining the correct orientation of the tool holder. A tool identification tag is provided at 101.
The pot 105 is integrally formed with an arm 103. The arm 103 projects radially from the side of the pot body and terminates with a transversely extending section, upon which is fitted a rotatable pusher wheel 108 and a bearing 109. The pot is retained in the storage position shown in FIG. 4 by the action of the bearing 109, which bears against a bearing plate 125. The plate is provided with a local slot at the pot release position, thus enabling the pot to be rotated about the axis 117, when it is located there. The pusher wheel 108 is adapted to fit within a mouth 123 of a fork 122 mounted at the end of a rod 121 of a vertically aligned piston 120. As the carousel wheel rotates, the pusher wheel 108 of each pot assembly consecutively enters the mouth 123 of the fork 122 from the side. When the appropriate tool holder is in position, pneumatic cylinder 120 is actuated, so as to cause the piston rod 120 to extend vertically downwards. As this happens, the pusher wheel 108 is urged downwardly by virtue of the fact that it is constrained within the mouth 123 of the fork 122. This downward movement causes the pot 105 to rotate about the axis 117, thereby eventually bringing the tool holder into the position shown in chain-dotted line in FIG. 4. From this position, a transfer arm can transfer the tool to the machine head, as generally described in relation to FIGS. 1 to 3.